Ceramic honeycomb structures used for cleaning exhaust gases discharged from automobile engines, etc., are produced by extrusion-molding a moldable, plastic ceramic material comprising ceramic powder, a pore former, a molding aid such as a binder, water, etc. through a die member 50 as shown in FIGS. 4(a)-4(c), drying and sintering the resultant molding. In the extrusion molding, the moldable ceramic material is introduced into the molding die member 50 through moldable-material-supplying holes 51, and discharged as a honeycomb structure molding from grooves 52.
Because the grooves of the die member are extremely narrow, the repeated extrusion-molding of honeycomb structures results in clogging the grooves of the die member with foreign matter and high-hardness components in the moldable ceramic material. Because the use of a die member clogged with such foreign matter, etc. produces honeycomb structures with deteriorated quality, the periodic cleaning of the die member is needed. To clean this die member, a moldable ceramic material clogging holes and grooves should be removed together with foreign matter and high-hardness components. Thus used conventionally are a method of spraying high-pressure water only to holes, and a method of spraying high-pressure water only to grooves.
However, because the moldable ceramic material contains an organic binder, it cannot be sufficiently removed by spraying high-pressure water to only the holes or the grooves. When the high-pressure water is sprayed to the holes, the moldable ceramic material remaining in the grooves cannot be completely removed. On the other hand, when the high-pressure water is sprayed to the grooves, the pressure of the high-pressure water should be reduced to avoid troubles such as the deformation and damage of small grooves, or the die member is not sufficiently cleaned, or cleaning needs long time.
JP 2003-285014 A discloses a method for cleaning a die member by heating a die member having a molding material attached thereto at 200-500° C. to remove an organic binder from the molding material, and then spraying a fluid at a pressure of 40 kg/cm2 or less to the die member to remove the molding material. However, the cleaning method described in JP 2003-285014 A suffers the problem that the die member is deformed by heating at 200-500° C., failing to keep the desired groove width. Particularly in the case of large molding die members of 200 mm or more in outer diameter, this problem is serious.